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Conduit Bending calculator

Parallel Roll Offset Calculator

Professional rolling offset calculator for electricians. Calculates the true diagonal distance, roll angle, mark spacing, and shrinkage when conduit must move both horizontally AND vertically to clear an obstacle. Supports 22.5°, 30°, and 45° bend angles with EMT, IMC, and rigid conduit.

Updated June 21, 2026

Calculator Inputs

Side-to-side distance to move (inches)

Up/down distance to move (inches)

Distance from conduit end to first bend (inches)

Calculation Results

Enter values above to see calculation results

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Example Calculations

8" × 6" Rolling Offset at 30°

Standard rolling offset around an HVAC duct.

Inputs
  • Horizontal Offset: 8
  • Vertical Offset: 6
  • Bend Angle: 30 degrees

How to Use

Rolling Offset: The 3D Conduit Bend

A rolling offset is the most complex standard bend an electrician makes. Unlike a flat offset (moving only left/right or up/down), a rolling offset moves conduit in two planes simultaneously — requiring the bender to be rotated at a calculated angle. Get the math wrong and the conduit ends up twisted, misaligned, or short.

The Three Rolling Offset Formulas

Calculation Formula What It Gives You
True Offset√(horizontal² + vertical²)Actual diagonal distance the conduit travels
Roll Anglearctan(horizontal ÷ vertical)How much to rotate the bender from vertical
Mark SpacingTrue Offset × MultiplierDistance between bend marks on the conduit

Multipliers and Shrinkage by Bend Angle

Bend Angle Multiplier Shrinkage/inch of offset Best For
22.5°2.6133/16"Gentle bends in exposed areas, large conduit
30°2.0001/4"Most common — easy 2× multiplier for field math
45°1.4143/8"Tight spaces, short distances
60°1.1551/2"Very tight bends (rarely used)

Worked Example: Route Around HVAC Duct

A 3/4" EMT conduit running along a ceiling needs to move 8" to the right and 6" up to clear an HVAC duct, using 30° bends:

  • Step 1 — True Offset: √(8² + 6²) = √(64 + 36) = √100 = 10.0"
  • Step 2 — Roll Angle: arctan(8 ÷ 6) = arctan(1.333) = 53.1°
  • Step 3 — Mark Spacing: 10.0" × 2.0 (30° multiplier) = 20.0"
  • Step 4 — Shrinkage: 10.0" × 1/4" = 2.5" shorter overall

Bending sequence: Make the first 30° bend at mark 1. Rotate the conduit 53.1° clockwise. Make the second 30° bend at mark 2 in the opposite direction. The conduit now travels diagonally through both planes.

Pro Tips for Rolling Offsets

  • Mark a reference line: Draw a straight line along the full length of the conduit before bending. After making both bends, this line should be straight when viewed from the side — if it spirals, your roll angle was inconsistent between bends.
  • Use a torpedo level: Tape a torpedo level to the conduit to verify the roll angle before making the second bend.
  • Bend order matters: Always make the first bend first, rotate, then make the second bend. Don't try to pre-rotate before the first bend.
  • Spring-back compensation: For 1" EMT and larger, add 2–3° to each bend to compensate for spring-back. Check with a protractor after bending.
  • Field verification: Hold the conduit in position after the first bend to verify the roll angle is correct before making the second bend. It's much easier to adjust before bending than after.

Common Applications

HVAC obstacle clearance — route conduit around ductwork that requires both horizontal and vertical offset

Beam and pipe crossings — navigate obstacles mounted at angles to the conduit run

Panel approaches — enter panels at angles that require 3D offsets from the conduit rack

Ceiling height transitions — route conduit through areas where ceiling elevation changes

Exposed conduit runs — create professional-looking 3D bends in architectural and industrial installations

Equipment room routing — navigate around transformers, switchgear, and mechanical equipment

Parallel rack transitions — maintain uniform spacing when a conduit rack must change both height and position

Underground-to-above-ground transitions — route conduit from underground stubs to wall or ceiling runs

Frequently Asked Questions

What is a rolling offset and how is it different from a regular offset?
A regular offset moves conduit in one plane — either left/right OR up/down. It's a 2D bend. A rolling offset moves conduit in both planes simultaneously, creating a 3D diagonal path. This requires rotating (rolling) the bender to an angle between the two planes. The true offset distance is calculated using the Pythagorean theorem: √(horizontal² + vertical²), which is always larger than either individual dimension. Rolling offsets are needed when an obstacle forces conduit to move both horizontally and vertically at the same point.
How do I determine the roll angle for the bender?
Roll angle = arctan(horizontal distance ÷ vertical distance). This tells you how many degrees to rotate the bender from its normal vertical position. For equal horizontal and vertical distances, the roll angle is 45°. If horizontal > vertical, the angle exceeds 45° (conduit moves more sideways). If vertical > horizontal, the angle is less than 45° (conduit moves more up/down). Use the calculator for precise values — even a 5° error in roll angle causes noticeable misalignment at the end of the bend.
Why do my rolling offsets always come out twisted or misaligned?
The most common causes are: (1) inconsistent roll angle between the two bends — both bends must be rotated the exact same amount; (2) not rotating the conduit after the first bend before making the second — you must physically rotate the pipe by the roll angle; (3) spring-back in larger conduit sizes changing the effective bend angle; (4) measuring error in the mark spacing. Fix: draw a reference line along the conduit before bending and align both bends to it. After both bends, the reference line should appear straight when viewed from the side.
Which bend angle should I use for rolling offsets — 22.5°, 30°, or 45°?
Use 30° as your default — the 2× multiplier makes field math simple and the bend is moderate in force and appearance. Use 22.5° when: the conduit is exposed (gentler, more professional look), the conduit is 1-1/4" or larger (less force required), or the offset is large. Use 45° when: space is tight and you need to cover the offset in the shortest distance. Avoid 60° bends unless absolutely necessary — they require significant force and can kink thin-wall conduit.
How do I account for shrinkage in a rolling offset?
Shrinkage in a rolling offset is calculated using the TRUE offset distance (not the individual horizontal or vertical distances) multiplied by the shrinkage per inch for your bend angle. Example: True offset = 10", using 30° bends → shrinkage = 10 × 1/4" = 2.5". This means the conduit will be 2.5" shorter overall after bending. Add this to your cut length before bending. Shrinkage values: 22.5° = 3/16"/inch, 30° = 1/4"/inch, 45° = 3/8"/inch. For critical runs where the conduit must terminate at an exact point, always account for shrinkage.

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